1. Field of the Invention
The present invention relates to a method and device for tuning a first oscillator with a second oscillator and to a rotation rate sensor, which employs a method of this sort and/or a device of this type.
2. Prior Art
Different methods and devices are known, which handle detected signals numerically for evaluation of oscillatory signals of several oscillators, in order to consider amplitude errors, phase errors and the like. A signal analysis method, for example as described in DE-OS 196 53 020, is employed. Generally rotation rate sensors, which are used for Coriolis effect, are known in connection with systems for vehicle dynamic control in motor vehicles. The described rotation rate sensor comprises one or more masses, which are vibrationally excited by a voltage produced in an electrical circuit in the usual manner. The mechanical vibrations act on one or more acceleration sensors, which measure Coriolis acceleration acting on the vibrating masses. The rotation rates of the system can be determined from the excitation and acceleration signals with the help of a suitable analysis or evaluation circuit.
An additional electrical test signal, which is fed to the acceleration sensor or sensors, can also serve as an additional arbitrarily selected additional acceleration at the sensor. Thus, for example, information regarding the properties of the acceleration sensors and subsequently connected analysis circuit can be obtained. Thus it is also possible to detect errors, especially systematic errors. This is especially important since the rotation rate sensors evaluating the Coriolis effect have systematic errors, whose effect on the measured signal must be minimized by suitable selection of an analysis method. Oscillator frequencies that are as far apart as possible should be selected, so that the amplitude errors resulting from resonance rise and phase error are as small as possible, whereby electrical interference or cross-talk of the oscillator signal in the acceleration signal can be suppressed by phase-locked or -synchronized demodulation. Since the oscillator frequencies cannot be too far apart because of sensitivity losses, a certain residual error always remains present.
Analog and digital circuits are both used for signal processing for evaluation of the output signals of the rotation rate sensors. Those analysis circuits can determine the rotation rate and also still act to test the operation of the sensor or the evaluation circuit.
It is an object of the present invention to provide a method and device for analysis of vibrations or oscillations with a high precision and with small errors.
It is another object of the present invention to provide an improved rotation rate sensor of the above-described kind.
The method according to the invention for tuning a first oscillator to a second oscillator has the following steps:
a) generating two frequency-shifted and/or phase-shifted signals symmetric to an oscillation of the second oscillator;
b) exciting the first oscillator with the frequency-shifted and/or phase-shifted signals produced in step a);
c) determining a response behavior of the first oscillator to the frequency-shifted and/or phase-shifted signals produced in step a);
d) forming a difference signal from the respective response signals from the first oscillator, e.g. a phase difference signal or an amplitude difference signal; and
e) tuning the frequency and/or the phase of the first oscillator according to the difference signal.
Two oscillations can thus be tuned to each other (xe2x80x9cmatchedxe2x80x9d) by this method, so that, for example, a resonance rise is adjustable.
The first and second oscillators are preferably different, especially orthogonal modes of one and the same vibrating body. Thus, for example, a vibrating body with two degrees of freedom can be tuned or xe2x80x9cmatchedxe2x80x9d regarding its two oscillation modes. Alternatively, the method of course can be applied to two independent vibrating bodies and of course also with independent vibration directions.
The determination of the response behavior can occur in a particularly simple manner by means of detection of the amplitudes and/or phases of the oscillation of the first oscillator. These measured variables may be determined especially simply, e.g. by means of an acceleration sensor or the like means.
The tuning of the first oscillator occurs advantageously by shifting the eigenfrequency. An especially preferred method for shifting the eigenfrequency is the so-called electrostatic coupling, in which however other processes influence the vibration behavior, which are familiar to one skilled in the art. This latter method can be advantageously used to shift the eigenfrequency.
Finally, it is preferable that the method according to the invention is used as a regulating process, in which a repeated use of the process occurs to perform the control. Thus a permanent tuning (xe2x80x9cmatchingxe2x80x9d) can be obtained, which compensates also for temperature changes and other parameters, since the oscillations can always be automatically tuned to each other.
The device for tuning the first oscillator with a second oscillator includes means for generating two frequency-shifted, and/or phase-shifted signals symmetric to the oscillation of the second oscillator; means for ascertaining the response behavior of the first oscillator to the frequency-shifted and/or phase-shifted signals and for producing a difference signal according to this response behavior and a control means for tuning the frequency and/or phase of the first oscillator according to the difference signal. The control means is preferably a regulating device, which guarantees a permanent tuning of the oscillations of the two oscillators.
Advantageously the apparatus according to the invention is employed with different, especially orthogonal, modes of one vibrating body and also with several independently vibrating bodies that oscillate in different directions.
In a further embodiment the control or regulating device comprises an electrostatic coupling device, in order to be able to tune the vibration behavior of the first oscillator in an especially simple manner, so that the xe2x80x9cmatchingxe2x80x9d of the two oscillations is possible by applying an electrical signal. Understandably also other devices influencing the oscillatory behavior are useable with the device according to the invention, like, e.g., the synchronization of additional springs and the like.
The rotation rate sensors according to the invention are characterized by operating by performing the method for tuning a first oscillator with a second oscillator according to the invention or they include a device for tuning a first oscillator with a second oscillator according to the invention.
It should also be noted that the invention is not limited to mechanical vibrations and oscillators.